Principle of automatic adjustment of temperature of electric iron

The electric iron  is made using the thermal effect of electric current and is used to iron clothes. Due to the different materials of clothes, there are cotton, linen, silk, wool, chemical fiber, etc., so the temperature required for ironing is also different. Generally speaking, cotton fabrics are more resistant to high temperatures, followed by wool, and chemical fiber clothing is not resistant to high temperatures. How can we adapt to various requirements? Now there is a temperature-adjustable electric iron on the market, which can not only adjust various temperatures, but also keep the temperature constant at a certain temperature. In this way, when ironing a certain kind of clothing, as long as the temperature adjustment knob is adjusted to the temperature corresponding to the fabric, you can iron with confidence.

How to adjust the temperature of an electric iron? The credit goes to the automatic switch made of bimetal.

The bimetallic sheet is made of copper sheet and iron sheet with the same length and width. When heated, because the copper sheet expands more than the iron sheet, the bimetallic sheet bends toward the iron sheet. The higher the temperature, the more significant the bending.

At room temperature, the contacts on the ends of the bimetallic strip are in contact with the contacts on the elastic copper strip. When the iron head is connected to the power source, the current flows through the contacting copper sheet and bimetallic sheet, and flows through the heating wire. The heating wire generates heat and transfers the heat to the metal soleplate at the bottom of the iron. People can use the heating soleplate to iron. The clothes are ironed. As the energizing time increases, when the temperature of the bottom plate rises to the set temperature, the bimetallic strip fixed with the bottom plate is heated and bent downward, and the contact on the top of the bimetallic strip separates from the contact on the elastic copper sheet, so The circuit is broken. At this time, the temperature of the bottom plate no longer rises, and it decreases due to the heat dissipation of the bottom plate; the deformation of the bimetallic strip is gradually restored. When the temperature drops to a certain value, the bimetallic strip and the elastic copper sheet are in contact again, and the circuit is connected again , The temperature of the bottom plate began to rise again. In this way, the circuit is disconnected when the temperature is higher than the required temperature, and the circuit is connected when the temperature is lower than the required temperature, and the temperature can be kept within a certain range.

So, how to make the electric iron have different temperatures? When you turn the thermostat up, the upper and lower contacts move up accordingly. The bimetal only needs to bend slightly to separate the contacts. Obviously, the temperature of the bottom plate is relatively low at this time, and the bimetal can control the constant temperature of the bottom plate at a lower temperature. When you lower the temperature control knob, the upper and lower contacts move down accordingly, and the bimetal must be bent to a greater degree to separate the contacts. Obviously, the temperature of the bottom plate is relatively high at this time, and the bimetal can control the constant temperature of the bottom plate at a higher temperature. In this way, the requirements of the fabric for different temperatures can be adapted.